Method for the preparation of progressive-burning smokeless powder and product thereof



Patented Nov. 7, 1939 UNITED STATES METHOD FOR THE PREPARATIQN OF PRO-GRESSIVE-BURNING SMOKELESS POW- DER AND PRODUCT THEREOF Ellsworth S.Goodyear, Kenvil, N. 3., assignor to Hercules Powder Company,Wilmington, DeL, a corporation of Delaware No Drawing. ApplicationOctober 15, 1938, Serial No. 235,264

16 Claims.

This invention relates to an improved method for the preparation ofprogressive-burning double base smokeless powder and more particularlyto an improved method of coating double base smokeless powder usingdeterrent material and to the product so made.

In order to render possible, close control of the burning rate ofsmokeless powder and produce a high velocity of the projectile withouthigh 0 breech pressures, it has been customary to coat the grains of thesmokeless powder with a deterrent material, explosive or non-explosive,which will retard the initial burning rate of the powder grains. Suchcoating material penetrates the powder grains more or less, so that asthe powder burns, the successively exposed surfaces contain graduallyless and less of the deterrent material, thus causing the combustion ofthe grains to proceed with increasing speed.

It has been the general practice heretofore to coat double base powdersat relatively high temperatures, but this procedure has been open to anumber of objections, chief among which was the fact that powders socoated had a tendency to give high breech pressures when .fired at lowtemperatures. This is a serious disadvantage and while many attemptshave been made to improve this defect of prior art powders, none havemet with any appreciable success. It is the object of this invention toprovide a process of making a progressive-burning double base smokelesspowder which does not produce excessive breech pressures when fired atlow temperatures.

In accordance with my invention, I produce a progressive-burning doublebase smokeless powder in which the pressure increases usually obtainedwhen it is fired at low temperatures are largely or wholly eliminated byapplying to the smokeless powder at a temperature less than 55 C.preferably at a temperature from about C. to about 50 0., a deterrentmaterial which is a non-solvent for the nitrocellulose in the powder butcompatible therewith admixed with either a volatile or a non-volatilesolvent for said nitrocellulose.

The exact mechanism whereby the improvement is obtained by coating withmy deterrent combination at temperatures less than 55 C. is-

not known. It is believed that the excess heat in high temperaturecoating procedures affects the colloidal structure of the powder grainin a manner so as to weaken its strength, that is, it decreases itsresistance to shattering due to the shock of the primary explosiomand ofcourse the smaller the particles, the faster is their rate of burning.Whatever may be the mechanism, however, the results clearly show thatpressure increases due to the firing of the powder at subzez'otemperatures are practically completely eliminated by proceeding inaccordance with my process. I may, if so desired, extend the mixture ofa volatile or non-volatile solvent and the non-solvent deterrent with avolatile vehicle which is not a solvent for the smokeless powder grainssuch as benzene, ethyl alcohol, petroleum spirits and so forth, in orderto render the above said mixture more fluid and to cause it to come intomore intimate contact, and then subsequently remove this vehicle byevaporation. In general, I prefer applying the non-solvent deterrent insolution in a volatile solvent extended with a diluent of the typebefore mentioned, but in the case of certain types of powder,'wheregreater penetration of the coating is necessary to decrease the initialburning speed, without causing too great a difficulty of ignition, Iprefer to use a minimum amount of a non-volatile solvent for thesmokeless powder admixedwith a non-solvent deterrent both applied in asolution in a volatile solvent for the smokeless powder and a diluent.Alternatively, I may extend. the mixture of a volatile or non-volatilesolvent and a non-volatile deterrent by forming an aqueous emulsionthereof with a suitable emulsifying agent. I may also form an aqueousemulsion of the volatile vehicle extended mixture above shown. Theparticular method used for rendering the above mixture more fluid willdepend on which is more convenient and desirable for the particulardeterrent and smokeless powder in question.

In using my process, it may also be desirable to add water near the endof my coating procedure in order to prevent the grains of powder fromadhering to each other. Near the end 01' the coating process a veryconcentrated solution remains on the powder grains, which on furtherevaporation causes the coating material to be deposited on the surfaceof the powder grain, resulting in the adherence of the grains to eachother. Now I have found that if water is added at this stage, that is,just before serious clustering begins, each grain will be surrounded bya film of water which greatly reduces the stickiness of the grains.Heating can then be continued either in the sweetie barrel, or in thedry house, to cause the penetration of this surface material into thegrain and thus avoid the formation of clusters.

As examples of deterrents which I' may utilize to coat the grains ofdouble base smokeless powder in accordance with this invention I may usethe alkyl esters of the'fatty acids, as, alkyl esters of ricinoleicacid, alkyl esters of polymerized ricinoleic acid, etc.; terpenephthalates; rosin esters, as monohydric esters of abietic acid,polyhydric alcohol esters of abietic acid, monohydric alcohol esters ofpimaric acid, polyhydric alcohol esters of pimaric acid syntheticlacquer resins as methyl abietate, ethyl abietate, hydrogenated methylabietate, hydrogenated ethyl abietate, ester gum, hydrogenated estergum, modified or unmodified glycerol-phthalate resin, oil modifiedphenol-formaldehyde type resins, glycerol sebacate, glycol sebacate,glycerol-glycol sebacate, modified or unmodified ethylene glycolterpinene maleic anhydride resins, modified or unmodified diethyleneglycol terpinene maleic anhydrlde resins, modified or unmodifiedtriethylene glycol terpinene maleic anhydride resins, modified orunmodified glycerol terpinene maleic anhydride resins, etc.

As examples of the non-volatile solvent materials which I may use withthe above mentioned deterrents, I may use the alkyl phthalates as forexample, diethyl phthalate, dibutyl phthalate, diamyl phthalate, etc.;alkylphthalyl alkylglycollates, as for example, butylphthalylbutylglycollate, ethylphthalyl ethylglycollate, etc.; substituted ureas,as for example, symmetrical diethyldiphenyl urea,. symmetricaldimethyldiphenyl urea, symmetrical ethylmethyldiphenyl urea, etc. alkyltartrates such as dibutyl tartrate, etc.; alkyl citrates such astriethyl citrate, etc.; adipates such as cyclohexanol adipate; and loweralkyl esters of benzoic acid such as ethyl and methylortho-benzoylbenzoate.

As examples of the volatile solvent materials which I may use with theabove mentioned deterrents, I may use ethyl acetate, butyl acetate,mixtures of alcohol and ether and any others having a solvent effect onthe nitrocellulose in the smokeless powders and having a boiling pointfrom about 35 C. to about 180 C., preferably from about 70 C. to about130 C.

As illustrative of my invention I may coat 100 parts by weight of atubular grain double base rifie powder at a temperature less than about55 0., preferably at a temperature about 10 ,C. to about 50 C. withbetween about 0.5 to about 10 parts by weight of a mixture comprising25% to 95% of a deterrent, non-volatile and nonexplosive and which is anon-solvent for the nitrocellulose but compatible therewith and 5% to75% of a non-volatile non-explosive solvent plasticizer for; thenitrocellulose, said mixture being dissolved in 3parts to 50 parts byweight of a volatile vehicle having substantially no solvent action onthe nitrocellulose. In place of the non-volatile non-explosive solventplasticizer, I may use a volatile solvent for the nitrocellulose.

Alternatively, I may coat 100 parts by weight of a tubular grain doublebase smokeless powder, suitable for use in high powered rifles, at thesame temperatures as above shown, with between about 0.5 part to about10 parts by weight of a mixture comprising 25% to 95% of a deterrent,non-volatile and non-explosive and which is a non-solvent for thenitrocellulose but compatible therewith and 5% to 75% of a non-volatile,non-explosive solvent plasticizer for the nitrocellulosejsaid mixturebeing emulsified in 3 to 50 parts by weight of an aqueous solution ofwatersoluble carbohydrate ether, such as for example, methyl cellulose.vIn place of the non-volatile,

non-explosive solvent plasticizer, I may also use a volatile solvent forthe nitrocellulose.

As another illustration, I may coat 100 parts by weight of a tubulargrain double base smokeless powder, suitable for use in high poweredrifles at the same temperatures as above mentioned, with between about0.5 part to about 10 parts by weight of a deterrent, non-volatile andnon-explosive which is a non-solvent for the nitrocellulose butcompatible therewith dissolved in 1 part to parts by weight of avolatile solvent for nitrocellulose and 3 parts to 50 parts by weight ofa volatile vehicle which is a nonsolvent for the powder. Alternatively,instead of the non-solvent vvolatile vehicle, I may use 3 parts to 50parts by weight of an aqueous solution of methyl cellulose and apply theabove mixture in the form of an emulsion.

As a further illustration I may coat 100 parts by weight of a tubulargrain double base smokeless powder suitable for use in high poweredrifles with between about .5 part to about 10 parts by weight of amixture comprising to 95% of a deterrent, non-volatile and non-explosiveand which is a non-solvent for the nitrocellulose but compatibletherewith and between about 5% to about '75% of a non-volatile solventplasticizer for the nitrocellulose, 100'parts by weight of said mixturebeing dissolved in 50 parts to 300 parts by weight of a volatile solventfor the nitrocellulose, This solution may be extended with a volatilevehicle or emulsified as described in the modifications as above. Theamount of volatile solvent used will depend on the type of powder, thedegree of penetration desired, and the amount of deterrent used.

Powder grains may be coated in any convene ient apparatus, for example,in a sweetie barrel and after coating may be removed to a dry house forseveral days, then glazed with graphite and screened to remove anycoarse or fine material. The time of coating will depend upon the typeof powder coated and the results desired and may vary anywhere from 15minutes to 6 hours, but in general will vary from about minutes to about2 hours.

Having described my invention in a general manner, I will now proceed toa more detailed description by reference to the following exam- D 65:

Example 1 I Four hundred and fifty-three parts by weight of smokelesspowder containing 20% nitroglycerine are pressed through a .041. inchdie having a .015 inch pin, the resulting strands being cut into 21pellets per inch. These smokeless powder grains are placed in a sweetiebarrel and to them are added 3.9 parts by weight of butylacetylriclnoleate and 3.9 parts by weight of ethyl ortho-benzoylbenzoatedissolved in 80 parts by weight of 95% ethyl alcohol. The powder is thentumbled in the sweetie barrel with a coating solution for hour at 40 C.It is then dried, graphlted and screened to remove coarse and fineparticles. This powder when fired in a .30 caliber gun using a 170 grainbullet at a temperature of --47 F. gave an average breech pressure ofonly 6,700 pounds per square inch higher than when fired at 76 F.

The same powder coated in an identical manner except that a coatingtemperature of 60 C. is used, when fired in the same manner at 47 F.gave a breech pressure 36,300 pounds per square inch higher than whenfired at 76 F.

Example 2 Fifty parts by weight of the powder in Example 1, with thesame granulation, is coated with 0.5 part by weight of wood rosin and0.65 part by weight of ethyl ortho-benzoylbenzoate dissolved in 6 partsby weight of 95% alcohol and 0.75 part by weight of butyl acetate. Thispowder was tumbled in the sweetie barrel with the deterrent solution for45 minutes at C., removed therefrom, dried, graphited, and screened.This powder when fired in a .30 caliber cartridge with a 170 grainbullet at 40 F. gave a breech pressure 300 pounds per square inch lowerthan when fired at 82 F. Y

Example 3 Nine hundred and six parts by weight of the same base powderas in Example 1 and of the same granulation, was coated with 10 parts byweight of wood rosin dissolved in 18.1 parts by weight of secondarybutyl acetate and 120 parts by weight of ethyl alcohol. This powder wastumbled in the sweetie barrel with the coating solution for minutes at40 C., removed therefrom, dried, graphited, and screened. This powderwhen fired in a .30 caliber cartridge with a 110 grain bullet at atemperature of 42 F. gave a breech pressure 2,100 pounds per square inchhigher than when fired at 80 F.

Example 4.

Example 5 The same powder as in Example 4 was treat% in the mannerindicated in Example 4 by using a coating temperature of C.

Example 6 Treatment the same as in Example lbut using a coatingtemperature of 60 C.

Example 7 Treatment the same as in Example 4 but using a coatingtemperature of 70 C.

Powders made as shown in Examples 4-7 inclusive when fired in a .30caliber cartridge with a 1'70 grain bullet show the followingcharacteristics. It should be noted in the following table that thevelocities shown are instrumental velocities determined over a 150 footrange.

Mean Max Example Charge Velocity prespreslzowder sure sure By coatingsmokeless powder according my process, as illustrated in the aboveexamples, it

is apparent that the powders coated with my deterrent mixtures attemperatures less than C. produce breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when the.

same powder is fired at ordinary temperatures.

It will be understood that where I have referred to a compound as beinga non-solvent for nitrocellulose, I mean a compound which, by reason ofits relatively low content of chemical groups,

which are known to promote solvent action, its high molecular weight,its high viscosity at temperatures to which the compound may besubjected, or its structural arrangement, does not dissolvenitrocellulose of the degree of nitration.

used in a particular case at a measurable rate of solution.

It will be understood that the details and examples hereinabove setforth are illustrative only and that the invention as herein broadlyde-i scribed and claimed is in noway limited thereby.

This application is a continuation-in-part of my application Serial No.152,269, filed July 6, 1937.

What I claim and desire to Patent is:

1. A method of .preparation of progressiveburning, double base smokelesspowder, characterized by producing breech pressures when fired .atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures, which comprises coatingdouble base smokeless powder grains at a. temperature less than about 55C. with an admixture of a non-volatile, non-explosive organic.

material which is a non-solvent for the nitrocellulose but compatibletherewith and a solvent for said nitrocellulose.

2. A method of preparation of progressiveburning, double base smokelesspowder, characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures, which comprises coatingdouble base smokeless powder grains, at a temperatures less than about55 C., with an admixture of an alkyl ester of a higher fatty acid and asolvent for said nitrocellulose.

3. A method of preparation of progressiveburning, double base smokelesspowder, characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures, which comprises coatingdouble base smokeless powder grains, at a temperature less than about 55C., with an admixture of an alkyl ester of ricinoleic acid and a solventfor nitrocellulose.

4. A method of preparation of progressiveburning, double base smokelesspowder, char-- protect by Letters.

stantially greater than those produced when fired at ordinarytemperatures, which comprises coating double base smokeless powdergrains, at a temperature less than about 55 C., with an admixture ofbutylacetyl ricinoleate and a solvent for nitrocellulose.

5. A method of preparation of progressiveburning, double base smokelesspowder, characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures, which comprises coatingdouble base smokeless powder grains, at

temperatures less than about C., with an admixture of rosin and asolvent for nitrocellulose.

6. A method of preparation of progressiveburning, double base smokelesspowder, characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures, which comprises coatingdouble base smokeless powder grains, at temperatures less than about 55C., with an admixture of rosin and a lower alkyl ester of benzoylbenzoicacid.

'7. A method of preparation of progressiveburning, double base smokelesspowder, characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures, which comprises coatingdouble base smokeless powder grains, at temperatures less than about 55C., with an admixture of rosin and ethyl ortho-benzoylbenzoate.

8. A method of preparation of progressiveburning, double base smokelesspowder characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures which comprises coatingdouble base smokeless powder grains at a temperature less than about 55C. with an admixture of rosin and butyl acetate.

9. A double base smokeless powder coated with an admixture of anon-volatile, non-explosive organic materials which is a non-solvent forthe nitrocellulose but compatible therewith and a non-volatile solventfor said nitrocellulose, said coated smokeless powder beingprogressive-burning and being characterized by producing breechpressures when fired at sub-zero temperatures which are notsubstantially greater than those produced when fired at ordinarytemperatures.

10. A double base smokeless powder coated with an admixture of an alkylester of a higher fatty acid and a non-volatile solvent for thenitrocellulose, said coated smokeless powder being progressive-burningand being characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures.

11. A double base smokeless powder coated with an admixture of an alkylester or ricinoleic acid and a non-volatile solvent for thenitrocellulose, said coated smokeless powder being progressiveburningand being characterized by producing breech pressures when fired atsub-zero temperatures which are not substantially greater than thoseproduced when fired at ordinary temperatures.

12. A double base smokeless powder coated with an admixture of butylacetyl ricinoleate and a non-volatile solvent for the nitrocellulose,said coated smokeless powder being progressiveburning and beingcharacterized by producing breech pressures when fired at sub-zerotemperatures which are not substantially greater than those producedwhen fired at ordinary temperatures.

13. A double base smokeless powder coated with an admixture of rosin anda non-volatile solvent for the nitrocellulose, said coated smokelesspowder being progressive-burning and being characterized by producingbreech pressures when fired at sub-zero temperatures which are notsubstantially greater than those produced when fired at ordinarytemperatures.

14. A double base smokeless powder coated with an admixture of rosin anda lower alkyl ester of benzoylbenzoic acid, said coated smokeless powderbeing progressive-burning and being characterized by producing breechpressures when fired at sub-zero temperatures which are notsubstantially greater than those produced when fired at ordinarytemperatures.

15. A double base smokeless powder coated with an admixture of rosin andethyl ortho-benzoylbenzoate, said coated smokeless powder beingprogressive-burning and being characterized by producing breechpressures when fired at subzero temperatures which are not substantiallygreater than those produced when fired at ordinary temperatures.

16. A double base smokeless powder coated with an admixture of butylacetyl ricinoleate and ethyl ortho-benzoylbenzoate, said coatedsmokeless powder being progressive-burning and being characterized byproducing breech pressures when fired at sub-zero temperatures which arenot substantially greater than those produced when fired at ordinarytemperatures.

' ELLSWORTH S. GOODYEAR.

